It behooves Nintendo to insist that the Nintendo 3DS is first and foremost about playing video games. That way, when a feature like Netflix streaming comes along, it’s a surprise instead of an expectation.

Netflix streaming was the big news from Nintendo’s Game Developers Conference keynote on Wednesday. The feature will arrive during the summer, at least a few months after the Nintendo 3DS’s March 27 launch.

This has been a delicate balancing act for Nintendo. When the company introduced the 3DS at last year’s E3 trade show, it brought a handful of 3D movie trailers from Disney, Warner Bros. and Dreamworks, but was careful to say that it hadn’t inked any content deals. The story was the same in January, when I got a lengthier 3DS demonstration during the Consumer Electronics Show. Nintendo reps told me they weren’t announcing any 3D movies, but showed off a trailer nonetheless. At GDC, Nintendo said it will offer 3D music videos, movie trailers and other short-form content, but said nothing about full-length movies.

If Nintendo positions the 3DS is more than just a gaming device, it’ll face pressure to do a lot more than it’s doing now. Users would wonder why there isn’t a storefront for movies, both 2D and 3D. They’d expect that the videos and photos they capture would be shareable in 2D on sites like Flickr and YouTube, and not just with other 3DS users. (It’s unclear whether the Nintendo DSi’s Facebook photo sharing feature will be available on the 3DS.) You’d see more comparisons to the iPod Touch.

But with a little bit of spin, Nintendo can cast Netflix as a bonus feature, take it or leave it. Most of the time, you’re supposed to be playing video games on the thing.